1. Field of the Invention
This invention relates to the field of gear shift mechanisms for automotive transmissions It more particularly pertains to a mechanism for sliding gear engagement, especiallY for reverse drive
2. Description of the Prior Art
In manual transmissions that produce unsynchronized reverse drive engagement, an idler gear is moved by the shift mechanism along a support shaft into engagement with a pinion and gear to produce reverse drive. U.S. Pat. No. 4,307,624 describes a shift mechanism that produces this result in a longitudinal disposed transmission, in which the input shaft and output shaft are mutually coaxial and aligned with the engine and rear drive shaft. U.S. Pat. Nos. 4,297,910 and 4,310,692 described shift mechanisms for actuating sliding gear engagement in four-speed ratio transaxle having four speed ratios. U.S. Pat. Nos. 4,377,093 and 4,799,399 describe shift mechanisms for actuating reverse gear engagement in a five-speed transaxle.
In each of these transmissions, the shift mechanism operates under the control of the vehicle operator to pivot a bellcrank having one arm continually engaging a reverse idler and adapted to slide the idler on its support shaft when the bellcrank pivots. As the operator moves the gear selector shaft among several shift planes, and within each shift plane between gear engagement positions, a selector pin rotates and translates, its movement corresponding to that of the gear selector shaft. When the gear selector is moved to the reverse shift plane, the selector pin rotates into engagement with the reverse bellcrank. As the operator moves the gear selector to the reverse drive position, the selector pin moves axially, thereby causing the bellcrank to pivot and slide the reverse idler into engagement with a reverse pinion and reverse gear. This action completes the reverse drive torque delivery path between the engine crank shaft and transmission output shaft.
In each of these shift mechanisms the bellcrank pivots from its neutral position after the shift lever moves entirely into the reverse shift plane, and following movement from the neutral position to the reverse drive position. This requires that the shift selector be moved entirely to the reverse drive position within the reverse shift plane before the reverse idler becomes fully engaged with the reverse pinion and output gear.